Define CMAKE_OSX_DEPLOYMENT_TARGET CMake option + environment

src/py_build_cmake/commands/cmake.py

@@ -114,6 +114,9 @@ def prepare_environment(self):
             if self.install_settings.prefix is not None:
                 install_prefix = str(self.install_settings.prefix)
                 self.environment[f"{pbc}_INSTALL_PREFIX"] = install_prefix
+            if not self.cross_compiling() and self.plat.machine == "Darwin":
+                version = self.plat.macos_version_str
+                self.environment["MACOSX_DEPLOYMENT_TARGET"] = version
             if self.conf_settings.environment:
                 for k, v in self.conf_settings.environment.items():
                     templ = Template(v)
@@ -282,11 +285,14 @@ def get_configure_options_make(self) -> list[Option]:
 
     def get_configure_options_toolchain(self) -> list[str]:
         """Sets CMAKE_TOOLCHAIN_FILE."""
-        return (
-            ["CMAKE_TOOLCHAIN_FILE:FILEPATH=" + str(self.conf_settings.toolchain_file)]
-            if self.conf_settings.toolchain_file
-            else []
-        )
+        opts = []
+        if not self.cross_compiling() and self.plat.machine == "Darwin":
+            version = self.plat.macos_version_str
+            opts += ["CMAKE_OSX_DEPLOYMENT_TARGET:STRING=" + version]
+        if self.conf_settings.toolchain_file:
+            toolchain = str(self.conf_settings.toolchain_file)
+            opts += ["CMAKE_TOOLCHAIN_FILE:FILEPATH=" + toolchain]
+        return opts
 
     def get_configure_options_settings(self) -> list[str]:
         return [k + "=" + v for k, v in self.conf_settings.options.items()]

src/py_build_cmake/common/platform.py

@@ -69,6 +69,11 @@ class BuildPlatformInfo:
     macos_version: tuple[int, int] | None = None
     cmake_generator_platform: str | None = None
 
+    @property
+    def macos_version_str(self) -> str:
+        assert self.macos_version is not None
+        return ".".join(map(str, self.macos_version))
+
     @property
     def os_name(self) -> OSIdentifier:
         """Get the name of the current platform. For use in file names etc.,

src/py_build_cmake/config/quirks/macos.py

@@ -17,20 +17,24 @@ def cross_compile_mac(plat: BuildPlatformInfo, config: ValueReference):
     """Update the configuration to include a cross-compilation configuration
     that builds for the given architectures."""
     assert plat.archs is not None
+    assert plat.macos_version is not None
     assert not config.is_value_set("cross")
     logger.info(
         "ARCHFLAGS was specified. Automatically enabling cross-compilation for %s (native platform: %s)",
         ", ".join(plat.archs),
         plat.machine,
     )
     all = MultiConfigOption.default_index
+    macos_version = plat.macos_version_str
     options = {
         "CMAKE_SYSTEM_NAME": CMakeOption.create("Darwin", "STRING"),
         "CMAKE_OSX_ARCHITECTURES": CMakeOption.create(list(plat.archs), "STRING"),
+        "CMAKE_OSX_DEPLOYMENT_TARGET": CMakeOption.create(macos_version, "STRING"),
     }
+    env = {"MACOSX_DEPLOYMENT_TARGET": macos_version}
     cross_cfg: dict[str, Any] = {
         "os": "mac",
-        "cmake": {all: {"options": options}},
+        "cmake": {all: {"options": options, "env": env}},
     }
     cross_cfg["arch"] = StringOption.create(plat.platform_tag)
     # The SETUPTOOLS_EXT_SUFFIX variable is used by e.g. pybind11